Method for processing discharge devices



June 15, 1965 G. s. EVANS 3,139,396

METHOD FOR PROCESSING vDISGHARGE DEVICES Filed March 8. 1960 FIG. 2.

T0 MOTOR TO H IGH FR EQUENCY 6 EN E'RATOR United States Patent Ofi ice 3,189,396 lVlETHGD M393. PRQCESSENG DESQHARGE DEVEQES George S. Evans, (Ialdweii, Ni, assignor to Westinghouse Eiectric (Importation, East Pittsburgh, Pa, a corporation of Pennsylvania Filed Mar. 3, 1969, Ser. No. 13,564 11 Qiaims. (til. 3i625) This invention relates to seasoning discharge devices and, more particularly, to a method of seasoning fluorescent lamps and the resulting product.

In the manufacture of fluorescent lamps, the phosphor material is first applied to the interior surface of the envelope. Thereafter the lamp mounts which carry the electrodes are sealed into the ends of the envelope. The envelope is exhausted and the electrodes are treated by electrical heating to convert the alkaline-earth carbonates to oxides. After electrode treatment, a small charge of mercury and an inert ionizable gas are inserted into the envelope. The envelope is then tipped off or sealed and base caps are affixed to the ends thereof to facilitate lamp electrical connection. Such a manufacturing procedure is conventional. Every fluorescent lamp after exhaust, mercury and gas fill and tip off has remaining therein some degree of gaseous contaminants such as carbon dioxide, carbon monoxide, nitrogen and other residual molecular gases. These result in increasing the lamp starting voltage. taminants, the lamp is operated for a period such as three minutes. This initial operation, which essentially forms a part of the lamp manufacturing procedure, is. termed lamp seasoning. In this seasoning, operation of the lamp causes the internal lamp components such as the mercury fill, phosphor, leadwires, etc., to getter and fix, either chemically or mechanically, the residual gaseous contaminants. The exact mechanism by which these residual contaminants are gettered is not clear at this time. The lamp seasoning rate can be accelerated by increasing the lamp operating current, but the permissible lamp current is limited by possible damage to the electrodes resulting from operation at excessive currents. With high speed production, it is desirable to decrease the time required for the seasoning operation.

It is the general object of the present invention to provide an improved method for seasoning a discharge device. It is another object to provide an improved method for seasoning a fluorescent lamp in order to obtain a predetermined lowered lamp starting voltage.

It is a further object to provide an improved method for seasoning a fluorescent lamp, which seasoning can be conducted in very rapid fashion.

It is an additional object to provide an improved method for seasoning a fluorescent lamp wherein the lamp can be operated in such manner as to getter the residual impurities in rapid fashion without damaging the lamp electrodes.

It is still another object to provide a discharge device which has been seasoned in rapid fashion.

The aforesaid objects of the invention, and other objects which will become apparent as the description proceeds, are achieved by providing a method for seasoning a discharge device after fabrication and before installation in order to obtain a predetermined lowered lam-p starting voltage. In thismethod, at least that portion of the device in which a discharge occurs during normal operation is placed within the influence of a discharge-exciting, high-frequency electrode magnetic field having a predetermined intensity. This device excitation is maintained for a predetermined period of time. There is also providedthe resulting device which has been seasoned in accordance with the foregoing method.

In order to remove these residual conthe output coil 32. The fabricated lamp it? can be mann of 450 kilocycles, the resulting electric field generated at For a better understanding of the invention, reference should be had to the accompanying drawings wherein FIG. 1 shows a fluorescent lamp, partly in section, which has been processed in accordance with the present invention; r

FIG. 2 is a perspective view of an apparatus suitable for seasoning discharge devices in accordance with the present invention.

Although the principles of the invention are broadly applicable to any discharge device, the invention has particular utility with respect to fluorescent lamps such as a 40 w. T12 type and hence this type lamp has been so illustrated and will be so described.

With specific reference to the form of the invention illustrated in the drawings, the numeral 10 indicates gen-. erally a 40 w. Tl2-type fluorescent lamp comprising a sealed, light-transmitting tubular envelope 12 having mounts l4 sealed into either end thereof. The envelope terminates in base caps 16 to facilitate lamp support and electrical connection, as is customary. Each mount 14 comprises a stem portion 18 supporting lead-in conductors 20 sealed therethrough and extending into the envelope 12. Coiled tungsten or other suitable refractory metal coils 22 carrying electron-emission material such as alkaline-earth oxides are supported proximate the ends of the envelope 12 and are carried between the inwardly-extending extremities of the lead-in conductors 20. As a specific example, the electron-emission material comprises 60% BaO, 30% C210 and 10% SrO by weight. Base pins 24 are affixed to the base caps 16 and electrically connect to the lead-in conductors 2% in order to facilitate energize.- tion of the lamp id. The envelope carries on its interior surface a coating 26 comprising phosphor material, which as an example is manganese-activated zinc silicate. Also contained within the envelope is a filling of inert, ionizable starting gas such as argon at a pressure of 4 mm. and a small charge of mercury 28.

As indicated hereinbefore, before seasoning the lamp is either substantially or completely fabricated. It should be understood that the lamp can be seasoned before the base caps 16 are aiiixed to the ends of the envelope 1?. and such a lamp is considered as fabricated as far as the present invention is concerned. Also, if the base caps are subject to excessive dielectric heating, the lamp is preferably seasoned without the base caps in. In accordance with the present invention, the fabricated lamp is placed into a conveyor trough 30 as shown in FIG. 2. The trough Si) is formed as two spaced sections and the output coil 32 of a high-frequency generator (not shown) is placed between the spaced sections of the trough 39 so that any lamp which is moved therealong passes through ally 'moved through the conveyor trough 30 although preferably it is moved through the trough at a constant rate of speed by a motor drive (not shown) operating through a connecting cord 34. As the lamp it) passes through the output coil 32, the electromagnetic field existing within the coil 32 will cause a discharge to be generated Within the lamp section which is then passing through the coil. The electromagnetic field is controlled to have a predetermined intensity so that the gaseous atmosphere within the lamp 1d will be broken down and a mercury discharge created. As a specific example, the coil 32 is water cooled and has ten adjacent turns with an inside diameter of two inches, The current flowing theret hrough is approximately 60 amperes and the total coil length is two inches. With an exciting frequency the surface of the envelope 12 is approximately 9x10 volts per cm. This predetermined-intensity electromag netic field causes the excited portion of the lamp in to operate with a discharge intensity which is considerably greater than normally encountered with the usual or rated lamp Operating loading of 40 watts. For the specific lamp considered herein, the resulting ,dischargehas been observed to be approximately equivalent ,in intensity to the lamp overload discharge resulting when a current of one ampere is passed therethrough. As a result, residual contaminants within the lamp will be gettered by the mercur phosphor, envelope, etc. in rapid fashion. By way of further detail, with the foregoing specific electromagnetic field intensity, coil and lamp dimensions, the lamp it? is moved through the coil 32 at a rate of from 10 to 30 ftuper minute. With a lamp scanning rateof 24 ft; per minute, a four-foot-long 40 w. T12 lamp is completely moved through the coil in a period of ten seconds to complete the seasoningoperation.

As indicated hereinbefore, only that portion of, the lamp through which a discharge occurs duringnormal lamp operation need be subjected to the electromagnetic field. This can be readily accomplished by energizing the output coil 32 only when this indicated portion of the lamp is passing therethrough. From a production standpoint, however, it may be desirable to energize the output coil 32 continuously and to subject all portions of the lamp iii to the high frequency electromagnetic field. I

As a possible alternative embodiment, the lamp can be operated as it is passed through the high frequency coil by affixing additional lead conductors (not shown) to the base pins 24 and energizing the lamp it) with a conventional discharge, while additionally and simultaneously exciting the lamp with a high-frequency electromagnetic field as specified hereinbefore. If desired, the coil can be deenergized while such additional lead conductors connecting to the lamp 10 are passed through the coil 32 to avoid excessive heating effects.

Lamps processed in accordance with the present invention displayed a starting voltage averaging approximateiy 120 volts before seasoning. After seasoning,the starting voltage decreased to 90-94 volts. This is equivalent to the lowered starting voltage as is normally obtained with the conventional seasoning involving operatvision is made to limit the mercury-vapor pressure to enable the power input to the lamp to be increased without an appreciable sacrifice in efficiency.

The foregoing specific field used to excite the lamp is subject to considerable variation. In the example as given, the surface of the lamp envelope 12 as it traverses the coil 32 is separated therefrom by a distance of approximately one-quarter inch. A change in relative coil or lamp dimensions will require a different coil input in order that the field intensity at the surface of the envelope 12 is the same. Inaddition, the actual field intensity at the surface of the lamp envelope 12 can be varied considerably. The frequency of the applied electromagnetic field is also subject to considerable variation and a different frequency will normally necessitate an en tirely new set of operating conditions to duplicate the results obtained with the foregoing specific example. With higher frequency electromagnetic fields, lower power inputs are normally required in order to achieve equivalent results. As a further alternative, the output coil 32 can vary considerably in dimensions and can be sufficiently elongated so that it approximates or even exceeds the axial dimension of the lamp. With such a coil construction, the traverse of the lamp 110 through the coil 32 can be speeded up considerably to achieve equivalent results. A coil of smaller axial dimensions with an equivalent field applied theretoo will normally require that the traverse of the lamp it through the coil be slowed down an amount corresponding to the decrease in the axial coil dimensions. The output coil can also be formed as other than a hollow cylinder as shown in FIG. 2 and as described hereinbefore. As an example, the output coil can be provided with a semicylindrical configuration so that thelamp to be seasoned can be lifted in and out of the modified coil rather than axially passed therethrough.

It will be recognized that the objects of the invention have been achieved by providing an improved method for -seasoning discharge devices such as fluorescent lamps in order to obtain a predetermined lowered lamp starting voltage. This improved seasoning method can be conducted in a very rapid fashion Without damaging the lamp electrodes. In addition, there has been provided a discharge device which has been seasoned in very rapid fashion.

While a best embodiment of the invention has been illustrated and described hereinbefore, it is to, be particularly understood that the invention is not limited thereto or thereby.

I claim:

1. The method of seasoning a low-pressure discharge device after fabrication and ,before installation in order to obtain a predetermined lowered starting voltage, which method comprises, exciting all of that portion of the device through which a discharge occurs during normal operation with a discharge-exciting high-frequency electromagnetic field of predetermined intensity, and maintaining such electromagnetic field excitation of the device for a predetermined period of time.

2. The method of seasoning in rapid fashion a lowpressure discharge device after fabrication and before installation in order to obtain a predetermined. lowered starting voltage, which method comprises, exciting all of that portion of the device through which a discharge occurs during normal operation with a high-frequency electromagnetic field of predetermined intensity sufficient to create within said device a discharge. of predetermined greater intensity than encountered duringnormal device operation, and maintaining such electromagnetic field eX- citation of the device for a predetermined period of time.

3. The method of seasoning a fluorescent lamp after fabrication and before installation in order to obtain a predetermined lowered lamp starting voltage, said lamp adapted to be normallyoperated with a rated power loading to produce a discharge therein, which method comprises, exciting all of that portion. of the lamp through which a discharge occurs during normal lamp operation with a lamp-discharge-exciting high-frequency electromagnetic field of predetermined intensity, sulficient to produce in. said lamp a discharge of considerably greater intensity than encountered during normal rated operation of said lamp and maintaining such electromagneticfield excitation of the lamp for. a predetermined period of time suflicient to season said lamp.

4. The method of seasoning a fluorescent lamp after fabrication and before installation in order to obtain a predetermined lowered lamp starting voltage, said lamp adapted to be normally operated with a rated power loading to produce a discharge therein, which method comprises, placing the entire lamp within the influence of a lamp-discharge-exciting. high-frequency electromagnetic field of predetermined, intensity sufficient to produce in said lamp a discharge .of considerably greater intensity than encountered during normal rated operation of said lamp, and maintaining the entire lamp within the influencefof such electromagnetic field for a predetermined period of time suiiicient to season said lamp.

5-. The method of seasoning a fluorescent lamp after fabrication and before installation in order to obtain a predetermined lowered lamp starting voltage, said lamp adapted to be normally operated with a rated power loading to produce a discharge therein, which method comprises, exciting all of that portion of the lamp through which a discharge occurs during normal lamp operation with a high-frequency electromagnetic field of predetermined intensity sufficient to produce in said lamp a discharge of considerably greater intensity than encountered during normal rated operation of said lamp, maintaining such electromagnetic field excitation of the lamp for a predetermined period of time sutficient to season said lamp, and simultaneous with such lamp field excitation, applying to the electrodes of said lamp a preselected energizing potential of magnitude suflicient to support a normal lamp discharge.

6. The method of seasoning a fluorescent lamp after fabrication and before installation in order to obtain a predetermined lowered lamp starting voltage, said lamp adapted to be normally operated with a rated power loading to produce a discharge therein, which method cornprises, axially passing all of that portion of the lamp through which a discharge normally occurs during lamp operation through a lamp-discharge-exciting high-frequency electromagnetic field of predetermined intensity suificient to produce in said lamp a discharge of considerably greater intensity than encountered during normal rated operation of said lamp, and maintaining the discharge excited lamp portions within such electromagnetic field for a predetermined period of time sutficient to season said lamp.

7. The method of seasoning a fluorescent lamp after fabrication and before installation in order to obtain a predetermined lowered lamp starting voltage, said lamp adapted to be normally operated with a rated power loading to produce a discharge therein, which method comprises, axially passing the entire lamp through the influence of a lamp-discharge-exciting high-frequency electromagnetic field of predetermined intensity sufficient to produce in said lamp a discharge of considerably greater intensity than encountered during normal rated operation of said lamp, and maintaining the lamp within the infiuence of such electromagnetic field for a predetermined period of time sufiicient to season said lamp.

8. The method of seasoning a fluorescent lamp after fabrication and before installation in order to obtain a predetermined lowered lamp starting voltage, said lamp adapted to be normally operated with a rated power loading to produce a discharge therein, which method com prises, axially passing all of that portion of the lamp through which a discharge occurs during normal lamp operation through a lamp-discharge-exciting high-frequency electromagnetic field of predetermined intensity suflicient to produce in said lamp a discharge of considerably greater intensity than encountered during normal rated operation of said lamp, maintaining dischargeexcited lamp portions within such electromagnetic field for a predetermined period of time sufficient to season said lamp, and simultaneous with such lamp field excitation, applying to the electrodes of said lamp a preselected energizing potential of magnitude suflicient to support a normal lamp discharge.

9. The method of seasoning a fluorescent lamp after fabrication and before installation in order to obtain a predetermined lowered lamp-starting voltage, said lamp adapted to be normally operated with a rated power loading to produce a discharge therein, which method comprises, axially passing all of that preselected portion of said lamp in which a discharge occurs during normal lamp operation through a lamp-discharge-exciting high-frequency electromagnetic field of predetermined field intensity and having a limited dimension which is considerably less than the axial dimension of such preselected portion of said lamp to produce in said lamp a discharge of considerably greater intensity than encountered during normal rated operation of said lamp, and controlling the speed at which said lamp is axially passed through the electromagnetic field so that all portions of said lamp through which a discharge occurs during normal lamp operation are within the influence of the predetermined intensity electromagnetic field for a predetermined period of time sufficient to season said lamp.

in. The method of seasoning a fluorescent lamp after fabrication and before installation in order to obtain a predetermined lowered lamp-starting voltage, said lamp adapted to be normally operated with a rated power loading to produce a discharge therein, which method comprises, axially passing said lamp through a lamp-dischargeexciting high-frequency electromagnetic field of predetermined field intensity and having a limited dimension which is considerably less than the axial dimension of said lamp to produce in said lamp a discharge of considerably greater intensity than encountered during normal rated operation of said lamp, and controlling the speed at which said lamp is axially passed through the electromagnetic field so that at least substantially all portions of said lamp are within the influence of the predetermined intensity electromagntic field for a predetermined period of time suflicient to season said lamp.

11. The method of seasoning of fluorescent lamp after fabrication and before installation in order to obtain a predetermined lowered lamp-starting voltage, said lamp adapted to be normally operated with a rated power loading to produce a discharge therein, which method comprises, axially passing all of that preselected portion of said lamp in which a discharge occurs during normal lamp operation through a lamp-discharge-exciting highfirequency electromagnetic field of predetermined field intensity and having a limited dimension which is considerably less than the axial dimension of such preselected portion of said lamp to produce in said lamp a discharge of considerably greater intensity than encountered during normal rated operation of said lamp, controlling the speed at which said lamp is axially passed through the electromagnetic field so that all portions of said lamp through which a discharge occurs during normal lamp operation are within the influence of the predetermined intensity electromagnetic field for a predetermined period of time suflicient to season said lamp, and simultaneous with such lamp field excitation, applying to the electrodes 1 of said lamp a preselected energizing potential of magnitude sufiicient to support a normal lamp discharge.

References Cited by the Examiner UNITED STATES PATENTS Henry 313-177 X GEORGE N. WESTBY, Primary Examiner.

RALPH G. NILSON, ARTHUR GAUSS,

'B. G. MILLER, Examiners. 

1. THE METHOD OF SEASONING A LOW-PRESSURE DISCHARGE DEVICE AFTER FABRICATION AND BEFORE INSTALLATION IN OREER TO OBTAIN A PREDETERMINED LOWERED STARTING VOLTAGE, WHICH METHOD COMPRISES, EXCITING ALL OF THAT PORTION OF THE DEVICE THROUGH WHICH A DISCHARGE OCCURS DURING NORMAL OPERATION WITH A DISCHARGE-EXCITING HIGH-FREQUENCY ELECTROMAGNETIC FIELD OF PREDETERMINED INTENSITY, AND MAIN 